Endothelial permeability is increased by vascular endothelial cell growth factor and decreased by antioxidants. Whether or not l-ascorbic acid (Asc), which decreases endothelial permeability by stimulating the endothelial barrier function, is anti-angiogenic (angiostatic) remains unknown. We examined the role of Asc on angiogenesis using two assay systems. At first, the potential role of Asc on four steps of angiogenesis was investigated in cultured bovine microvascular endothelial cells. Asc inhibited the formation of vessel-like tubular structures of endothelial cells cultured on Matrigel; however, it did not decrease the activity of plasminogen activator (PA), which creates the space into which vascular vessels extend. Furthermore, even at high concentrations, Asc did not inhibit either the proliferation or migration of endothelial cell cultures. Secondly, whether Asc inhibited in vivo angiogenesis or not was studied on chick chorioallantoic membrane (CAM) during the 4-6 days of embryogenesis when neovascularization is rapid. It also revealed that angiogenesis was dose-dependently inhibited by Asc from 0.5 micro mol/CAM with half-maximal inhibition at 2.5 micro mol/CAM. Because it was previously reported that the endothelial barrier function decreases permeability via the stimulation of collagen synthesis induced by Asc, we treated CAM with the inhibitor of collagen synthesis, l-azetidine 2-carboxylic acid (AzC). This compound partially attenuated the angiostatic function of Asc on CAM. To understand the involvement of an antioxidant activity in the angiostatic function of Asc, we further examined the effect of glutathione (GSH), which is an endogenous antioxidant, on angiogenesis in CAM and endothelial cells. GSH inhibited CAM angiogenesis, as well as the formation of vessel-like tubular structures of endothelial cell cultures on Matrigel. Both Asc and GSH inhibited hydrogen peroxide (H(2)O(2)) induced tubular morphogenesis. These findings suggest that Asc affects angiogenesis through both its antioxidant properties and the stimulation of collagen synthesis. As the angiostatic activity of Asc may be one of the many effects involved in host resistance to the growth or invasiveness of solid cancer, it may be useful as a supplementary therapy in various angiogenic diseases.
When sucrose-dependent spectinomycin-resistant (Sucd-Spc') mutants of Escherichia coli were grown in the absence of sucrose, a new protein appeared in the membrane fraction insoluble in Triton X-100. The protein had a hydrophobic nature. However, unlike other outer membrane proteins the new protein was extracted with sodium dodecyl sarcosinate. The new protein was found to be identical with elongation factor Tu (EF-Tu), as judged from the electrophoretic mobility in three different gel systems, coprecipitation with the antiserum against EF-Tu, the profiles of peptide fragments produced with three different proteases and analyses of N-terminal and C-terminal amino acids. This membrane EFTu accounted for 5 -10 % of total cell EF-Tu. When spheroplasts were pretreated with trypsin, EF-Tu in the outer membrane disappeared. Incubation of cytosol EF-Tu with the outer membrane did not result in the binding of EF-Tu to the membrane. These results indicate that the appearance of EF-Tu in the outer membrane is not due to artificial binding during membrane preparation. It is suggested that the ribosomal alteration resulted in dislocation of the cytosol protein into the outer membrane.Sucrose-dependent spectinomycin-resistant (SuedSpc') mutants of Escherichia coli can grow in the presence of spectinomycin only when the medium is supplemented with 20 % (w/v) sucrose [l]. In a previous paper [2], we showed that an alteration in either protein S3, S 4 or S5 of the 30-S ribosomal subunits is responsible for the resistance to spectinomycin of SuedSpc' mutants. The mutation is pleiotropic, giving rise to hypersensitivity to antibiotics, dyes and detergents, abnormalities in cell morphology [l], and the
Alterations in the ribosomes of sucrose-dependent spectinomycin-resistant (Sucd-Spcr) mutants of Escherichia coli were studied. Subunit exchange experiments showed that 30S subunits were responsible for the resistance of ribosomes to spectinomycin in all Sucd-Spcr mutants tested. Proteins of 30S ribosomes were analyzed by carboxymethyl cellulose column chromatography based on their elution positions. Mutants YM22 and YM93 had an altered 30S ribosomal protein component, S5, and mutant YM50 had an altered protein, S4. Although a shift of elution position was not detected for all the 30S ribosomal proteins from mutant YM101, the amount of protein S3 was appreciably lowered in the isolated 30S subunits. A partial reconstitution experiment with protein S3 prepared from both the wild-type strain and YM101 revealed that the mutant had altered protein S3 which is responsible for the spectinomycin resistance. These alterations in 30S subunits are discussed in relation to the interaction between ribosomes and the cytoplasmic membrane.
Utilization of the 4-ƒÀ-galactosyl-lactose, O-ƒÀ-D-galactopyranosyl-(1•¨4)-0-ƒÀ-D-galactopyranosyl-(1•¨4)-D-glucopyranose, by the intestinal bacteria was investigated.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.